The present invention relates generally to satellite-based imaging systems, and more particularly, to a system and method for processing digitized images generated by a satellite-based imaging system to locate landmarks in the images that are used to automatically determine the position and attitude of the imaging system.
The assignee of the present invention has developed and deployed a Geostationary Operational Environmental Satellite (GOES) satellite that contains an imaging system that operates in both the visible and infrared regions of the spectrum and generates digitized images of the Earth. The digitized images generated by the imaging system are used for a variety of purposes, such as monitoring and analyzing flash floods and determining wind velocity by tracking cloud motion, for example.
To properly utilize the digitized images of the Earth, it is important to precisely know the location of the image pixels on the Earth. Accurate, stable image registration requires that orbit and attitude parameters of the satellite on which the imaging system is located be determined with great precision. These parameters can be derived by fitting line and pixel image coordinates of salient features, or landmarks, to their known latitude, longitude, and height on the Earth.
Registration accuracy of the images generated by the imaging system is accomplished by automatically determining the positions in the digitized images of landmarks on the Earth having known geodetic coordinates. The image analysis process measures offset error values indicative of the misregistration between the actual position of the landmarks in the digitized images and the desired position of the landmarks, and these offset error values are used to adjust the optical line of sight of the imaging system to produce optimum registration.
In the past, the position of a landmarks in a digitized images was automatically determined using reference images derived from previously acquired digitized images containing the landmark that were matched to the landmark in the currently processed digitized image. This approach has two problems. The exact position of the reference image was not known with subpixel accuracy. Also, several different reference images were needed to match landmarks contained in the currently processed image when the reference images were obtained under different diurnal and seasonal conditions.
Accordingly, it is an objective of the present invention to provide for a system and method for processing a digitized image generated by a satellite-based imaging system for measuring error values that are indicative of the misregistration between the actual position of the landmarks in the digitized images and the desired position of the landmarks, which error values are used to adjust the optical line of sight of the imaging system to produce optimum registration.